Known oral contraceptive regimens typically involve administering tablets containing a combination of estrogen and progestogen to an adult female over her menstrual cycle, usually followed by a "pill-free" or blank pill period. The amount of progestogen in the tablets of these regimens typically increases during the administration of the regimen. Alternatively, the amount of progestogen may remain fixed, or reaches a peak and then declines.
For example in French Patent Application No. 2,223,018 to Ortho Pharmaceutical, a progestogen is administered from at least the fifth day to the twenty-fifth day of the menstrual cycle, the dosage of the progestogen being greater during the last seven days of administration than it is during the first seven days.
Another example of an oral contraceptive regimen which increases the amount of progestogen throughout the woman's menstrual cycle is described in European Patent Application No. 36,229 to Akzo, nv.
In Belgian Patent No. 892,801 to Syntex (U.S.A.) Inc., a method of treating menopause is described also involving an increase in the amount of progestogen administered during the regimen's cycle.
German Patent Application No. 3,229,612 to Syntex (U.S.A.) Inc. describes a contraceptive regimen wherein the amount of progestogen administered peaks at mid-cycle, but then decreases.
U.S. Pat. No. 4,292,315 to Vorys describes another contraceptive regimen having a mid-menstrual cycle peak of progestogen and then subsequently declines. In this regimen, during the first 7 days, no exogenous steroids are administered. During days 8 to 14, the tablets administered may contain only a progestogen (e.g. 0.35 milligrams ("mg") of norethindrone). During days 15 to 18, tablets containing both an estrogen and the progestogen (e.g. 0.35 mg of norethindrone) are administered. During days 19 to 25, tablets containing both an estrogen and a progestogen (e.g. 1.0 mg of norethindrone acetate, which is approximately twice as potent as norethindrone) are administered. Finally during days 26 to 28, tablets are administered in which the amount of estrogen and progestogen are at half the daily dosage of the preceding 7 tablets (e.g. 0.35 mg norethindrone).
Canadian Patent Application No. 2,000,438 to Akzo, nv describes a multiphasic oral contraceptive preparation containing a progestogen and an estrogen in a first phase, and a progestogen only in the second phase. The amount of progestogen in the second phase is less than that in the last dosage unit of the first phase. The first phase may be split-up into three sub-phases, each successive sub-phase having more progestogen than the one earlier.